The present invention pertains to internal combustion engines, and more particularly to a new and unique fuel injection system in which liquid hydrocarbon fuel is converted into high-temperature, high-pressure vapor, which is then injected into the combustion chamber at the peak of the compression stage, where it mixes with air and ignites for the power stroke.
Heretofore, virtually all internal combustion engines using liquid hydrocarbon fuel, such as gasoline or diesel oil, have utilized carburetors or fuel injectors to deliver the liquid fuel into the intake air, or into the combustion chamber, in the form of finely atomized mist, which is supposed to evaporate completely, with the result that some of the fuel is still in liquid form during the combustion stage, and because of this it burns incompletely, leaving a considerable amount of unburned fuel in the exhaust to pollute the atmosphere. This unburned fuel in the exhaust also means reduced efficiency, lower power output, and poor fuel consumption characteristics. Moreover, the heat of vaporization which goes into evaporating the fuel in the intake manifold or the combustion chamber is subtracted from the total heat of combustion, with the result that the heat available for expansion on the power stroke is decreased, with a corresponding reduction in power output and efficiency.
In the case of gasoline engines (e.g., Otto cycle), the compression ratio is limited to a maximum value of about 12 to 1, unless exotic fuels of extremely high octane rating are used, as detonation becomes a serious problem.
The only internal combustion engines that burn cleanly, without substantial quantities of unburned fuel in the exhaust are those that have been designed and/or modified to run on natural gas, or on a liquid hydrocarbon fuel (e.g., butane, propane, etc.) which is a gas at atmospheric pressure and is pressurized to make it liquid. While such engines are reasonably satisfactory for use in stationary installations where they can be connected to a municipal gas line or to high-pressure fuel tanks of ample size, they are not suitable for use in automotive vehicles, boats or aircraft. For automobiles, the use of heavy-walled, high-pressure tanks presents design problems, and pressurized fuel tanks are a great hazard in case of an accident. Moreover, the specialized fuel is expensive and not widely available, and the high-pressure tanks must be filled by special fuel transfer apparatus. Furthermore, such gaseous fuels limit the compression ratio of the engine, as they are not high octane fuels.
The diesel engine has some advantages over the gasoline engine. It is more economical of fuel, and it burns the fuel more cleanly, with less unburned hydrocarbon and less carbon monoxide in the exhaust. However, the diesel engine must have compression ratios above 16 to 1 in order to produce sufficient heat of compression to ignite the fuel, and this requires heavy construction, which is expensive.